The Anti-Surge Compressor Housing Works

An anti-surge housing is designed to prevent compressor surge. It is not designed to replace a BOV or a BCV. it does not relieve the shockwave made by slamming the throttle shut and sending 20+ psi worth of airflow backwards in the charge piping and stalling the compressor wheel. Its purposes to relieve pressure on the throttle. It is designed to move the surge line over on the compressor map. Thus the ANTI SURGE. Surge under WOT is 100X more destructive to a compressor wheel and bearing assembly. Both are still not good and improper for turbo health. Whether this 'works' for some people is besides the point.

Goto zen to know more.

A "race car" running systems in place to pull power when shifting or 'no lift shifting' dont run BOVs because a fully closed throttle blade after WOT at 20+ PSI of boost is rare.

A "street car" doing multiple aggressive WOT to closed throttle like most of you guys do every day absolutely must have a means to relieve intake pressure.

Surge Line: Surge is the left hand boundary of the compressor map and represents a region of flow instability. This region is characterized by mild flutter to wildly fluctuating boost from the compressor. Continued operation within this region can lead to premature turbo failure due to heavy thrust loading. Surge will decay once the turbo speed finally slows enough to reduce the boost and move the operating point back into the stable region. This situation is commonly addressed by using a Blow-Off Valve (BOV) or Bypass Compressor Valve (BCV). A BOV functions to vent intake pressure to atmosphere so that the mass flow ramps down smoothly, keeping the compressor out of surge. In the case of a recirculating bypass valve, the airflow is recirculated back to the compressor inlet.

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BOV or BCV: Using the proper blow off valve (BOV) or bypass compressor valve (BCV) affects the system performance. There are two main types to consider. 

1. MAP (Manifold Absolute Pressure) sensor uses either a vent to atmosphere valve or a recirculation valve.
– Connect signal line to manifold source
– Surge can occur if spring rate is too stiff

2. MAF (Mass Air Flow) sensor uses a recirculation (bypass) valve for best drivability.
– Connect signal line to manifold source
– Position valve close to the turbo outlet for best performance (if valve can handle high temp).
– Surge can occur if valve and/or outlet plumbing are restrictive.

Originally Posted by spence88mph Andy, compare the maps of the turbo you're looking at with and without anti surge and base your opinions there, I have heard it adds lag but I'm not sure. As you mentioned, at low boost levels I don't think this is a factor. Originally Posted by MikeD94 I'm not an expert in turbo graphs but as you can see the graph on the left has more effeciency range (i.e. fatter area within the curves). Also, surge happens when the turbo operates to the left of the most left curve. So, the surge is less likely to happen on the left graph at the same air flow for a given pressure ratio. This can happen when the turbo is too large for a given engine dispacement under certain condition such as when the turbo starts to build boost at low engine rpm creating a phenomena where more boost builds than the engine can ingest. I'm sure this happens rarely on our 930 since our engine is relatively large for typical turbos used on these cars. I hope my lame explanation helps. Originally Posted by TurboKraft On a more stock engine -- 7:1 pistons, stock ports, stock cams -- we have had surge on the dyno and on the road. The turbos boost up quickly and produce more airflow than the engine can use, thus the surge. It makes a real distinct shhh-shhh-shhh sound, and a honking or chirping sound in really bad instances. It's really hard on the turbocharger.